Solid state high resolution NMR techniques are used to study lipid bilayer structure and dynamics. 31P spectra of oriented monodomain dipalmitoyllecithin (DPL) bilayers yield information on head group orientation. Specifically the head group in DPL is extended parallel to the bilayer plane. 31P and 2H NMR studies of the DPL-cholesterol-water system indicate that phase boundaries exist at both 20 and 33 mole percent cholesterol and this work provides insight as to the physical changes which occur at these boundaries. BIBLIOGRAPHIC REFERENCE: R.G. Griffin, "Observation of the Effect of Water on the 31P Spectrum of Dipalmitoyllecithin," Jour. Amer. Chem. Soc., 98, 851 (1976).